The producer price index fell 0.8 percent last month, the steepest drop since May, the Labor Department said Thursday. That follows a 0.2 percent decline in October. The index measures the cost of goods before they reach the consumer.

Gas prices fell last month by the most in more than three years. Food prices, however, rose by the most in nearly two years, pushed higher by costlier beef and vegetables.

Beef prices jumped 8.2 percent, the biggest gain in four and a half years. Vegetable prices rose nearly 12 percent. Grocery stores may mark up the prices of those products in the coming months, but probably not by as much.

High unemployment and weak wage increases will make it hard for retailers to pass on all of the higher costs.

"With global economic growth anemic at best ... we foresee little impetus for significant, sustained upside pressure on core prices," Joshua Shapiro, chief economist at MFR Inc., said in a note to clients.

In the past year, wholesale prices have increased 1.5 percent. That's the lowest annual pace in four months.

Excluding volatile food and gas costs, wholesale prices ticked up 0.1 percent in November and 2.2 percent in the past year.